In the manufacture of cars, it is highly desirable for body panels, such as doors, for example, to have a uniform gap falling within a nominal size when the panels are fitted together. This condition is often difficult to achieve in practice and requires rigid statistical controls on the panel production and assembly in order to insure that quality can be maintained.
Several known methods have been used to measure seal gaps. One known method involves measuring gaps using clay and a scale. Portions of clay are placed on one of the surfaces. The second surface is brought into alignment with the first surface causing the clay to contract into the gap between the two surfaces. The clay is then removed, and the width is measured using a scale or caliper to determine the gap between the two surfaces. This method, as with any manual measuring system, is tedious, time consuming and susceptible to technician error or inconsistency of technique.
A second known method of measuring seal gaps involves obtaining digital measurements between parallel surfaces using a hand-held measurement instrument. This method utilizes a passive sensor system. A magnetic sensor generates a magnetic field, and the distance between two magnetic surfaces is determined based upon the disruption of the magnetic field caused by the proximity of one of the metal surfaces. The signal generated by the disruption in the magnetic field is transmitted to a converter by way of a cable. This cable is susceptible to damage. In addition, this measurement system is susceptible to errors caused by the orientation of the earth's magnetic field. Also, this system is not practicable for vehicle applications involving plastic body panels.
A device for measuring gap and flush is disclosed in U.S. Pat. No. 5,067,250, issued to Auweiler et al. The device includes a housing having a base with an application face which, in use, is placed on the surface of one of the parts. A probe projects from the housing and is movable against a return force in the direction of the housing. Electromechanical transducers are disposed within the housing for detecting the displacement of the probe. This device must be manually guided along the gap to be measured which may be tedious if done manually or may be expensive if done automatically. This device also includes moving parts which are less reliable than stationary parts. The moving parts may shift or wear after continuous use, thereby resulting in inaccurate gap measurements.
In summary, known techniques do not include a convenient and reliable system for measuring gaps between two surfaces. Still further, a need has developed to provide a system for measuring the gap between two non-parallel surfaces.